1. Field of the Invention
The present invention relates to a mobile communication system using a Push To Talk (PTT) scheme. More particularly, the present invention relates to a method for establishing a phone call during the PTT call traffic.
2. Description of the Related Art
The Push To Talk (PTT) is referred to as “a basic call traffic scheme” used for a walkie-talkie or Handheld Transceiver (HT). The PTT scheme allows a user to communicate with her/his counterpart by properly operating PTT buttons disposed on, for example, a walkie-talkie. Specifically, in an operation for communication based on the PTT scheme, the user simply presses the PTT button when talking to her/his counterpart, and releases the pressed PTT button when listening to her/his counterpart's talking. Such a PTT scheme provides one-to-one or one-to-multi party communication through which the users can simply and rapidly communicate with each other.
In recent years, conventional mobile communication systems have provided so called internet phone service such as a Voice over IP (VoIP) scheme in which a specific Internet Protocol (IP) has been pre-assigned to each of the terminals of the system. Similar to the walkie-talkie or HT, such a VoIP scheme can also allow the mobile communication terminals to communicate with each other in the form of mobile communication PTT service which is capable of providing one-to-one or one-to-multi communication.
Such a mobile communication PTT service can provide voice/data services through which multiple users or groups can communicate simultaneously with each other. In order to start the mobile communication PTT service, the user presses a PTT button disposed properly in the mobile communication terminal capable of providing the PTT service so that the PTT mobile communication terminal may send a PTT service request to a mobile communication network related therewith. Then, the mobile communication network denies or accepts the requested service to, in case of the acceptance, assign the requested resources based on the determination criterions such as availability of resources, priority of the requesting user, etc. If the requested service has been accepted, the mobile communication network sets up connections from among all the active users belonging to a certain user group. Consequently, the called mobile communication terminal outputs an alarm sound and message displays for indicating the received PTT call request to the corresponding called user who, then, recognizes the PTT call request to start speaking or communication with the calling user. After setting up a voice traffic connection, the user who has requested a voice service can send the voice information to the corresponding user who then can listen to the voice just sent.
As mentioned above, during such a mobile communication PTT service, anyone from among the mobile terminal users which have participated in the PTT communication may want to communicate with her or his counterpart through the general voice call (hereinafter referred to as “phone call”), not the PTT communication. In this case, however, the user who wants the general phone call must operate her or his mobile communication terminal to terminate the current PTT session and then search for the counterpart's phone number in an address record or its equivalent or write directly the desired phone number for starting the phone call. Specifically, the user who wants to change the current PTT call traffic into the general phone call has to input several keys by selecting several menus for performing the general phone call instead of the PTT call traffic. Therefore, in the prior art, it is time-consuming and tedious to perform the key inputs and the menu selections for connecting the general phone call.